\newcommand{\parentheses}[1]{\left( #1 \right)}
\newcommand{\brackets}[1]{\left[ #1 \right]}

\newcommand{\mean}[1][]{\overline{\sum #1}}

\newcommand{\fun}[2]{\text{#1}\of{#2}}
\newcommand{\of}[1]{\parentheses{#1}}

\newcommand{\dotproduct}[2]{\left\langle #1 , #2 \right\rangle}

\newcommand{\openinterval}[2]{\parentheses{#1, #2}}
\newcommand{\closedinterval}[2]{\brackets{#1, #2}}
